Installation of a computer program (including device drivers and plug-ins), is the act of making the program ready for execution. Because the process varies for each application and each computer, programs (including operating systems) often come with an installer, a specialized program responsible for doing whatever is needed for the program installation. An installation program or installer is a computer program that installs files, such as applications, drivers, or other software, onto a computer. Some installers are specifically made to install the files they contain; other installers are general-purpose and work by reading the contents of the computer program to be installed.
Some computer programs can be executed by simply copying them into a folder stored on a computer and executing them. Other programs are supplied in a form unsuitable for immediate execution and therefore need an installation procedure. Once installed, the program may be executed again and again, without the need to reinstall before each execution.